Creating journals on metal stock by the use of a manufacturing process known as forming is advantageous in comparison to other known manufacturing processes because less material is wasted and, in the circumstance where the metal stock is rotated during the forming process, the metal stock is exposed to less stress. Typically, forming includes two types of processes, compression forming and flow forming. Referencing FIG. 1A, compression forming involves using a combination of compression and tension to form a finished part 10 from a sheet metal disc 12, wherein the wall thickness S.sub.1 of the finished part 10 is the same as the wall thickness S.sub.0 of the sheet metal disc 12. Flow forming involves two different types of processes, shear forming and cylindrical flow forming. Referencing FIG. 1B, shear forming involves forming a finished part 14 from a sheet metal disc 16, where the wall thickness S.sub.1 of a portion of the finished part 14 changes and the wall thickness S.sub.0 of a portion of the finished part 14 stays the same as the wall thickness S.sub.0 of the sheet metal disc 16. Referencing FIG. 1C, cylindrical flow forming involves forming a journaled end 18 from an extruded tube 20, such as for example a tube 22 or a cup 24, which can be parallel-sided, tapered or radiused, wherein the ending inner diameter d.sub.I of the journaled end 18 is less than the starting inner diameter D.sub.I, and the ending wall thickness S.sub.1 of the journaled end 18 is less than the starting wall thickness S.sub.0.
Known methods for forming a journal on extruded tubes are limited. The use of said methods requires the use of special forming machinery which can be very expensive to acquire, and often require special ordering to meet the specific needs of the operator. Moreover, using forming machinery to form a journaled end on extruded tubing generally requires an operator to be specially trained in the operation of the machinery, and once trained, requires the operator to properly position an extruded tube within the forming machine, instruct the forming machine to undertake the forming operation, and remove the extruded tube from the forming machine after completing the forming operation. The forming operation usually takes place in an area of the machine which is not enclosed, and therefore the forming machine does not lend itself to the use of flood coolant during the forming operation. Following removal, additional manufacturing steps are necessary to finish the formed journaled end because the forming process usually results in a journaled end having an imprecise outer diameter. As a result, the formed journaled end usually undergoes additional processing, such as for example using a lathe to cut material away from the formed journaled end, to obtain a finished journaled end having a precise outer diameter.
A metal machining lathe, in contrast to special forming machinery, is relatively inexpensive and commonly used machine to process metal stock into finished parts. In this regard, a lathe can be used to create a journal on an extruded tube by cutting material away from the end of the extruded tube. The cutting operation usually takes place in an area of the lathe which is enclosed, and therefore the lathe lends itself to the use of flood coolant during the cutting operation. Referencing FIGS. 2A and 2B, a lathe can be used to create a journaled end 28 having an outer diameter D.sub.O on an extruded tube 26 having a wall thickness S.sub.0 by cutting the material away from the end of the extruded tube 26, thereby causing the extruded journal 26 to have a wall thickness S.sub.1 at the journaled end 28. However, the process for creating the journaled end 28 using the lathe as described counters the advantage of using a forming manufacturing process. The lathe cuts away material from the extruded tube 26 to create the journaled end 28, thereby causing waste. Additionally, as can be seen in FIG. 2B, the use of a lathe to create a journaled end requires the extruded tube to have a starting wall thickness that is of a greater starting wall thickness that would otherwise be necessary if the journaled end was formed using a forming process. As a result, the finished part, which includes the extruded tube and journaled end, has more overall mass because the starting inner diameter d.sub.I of the extruded tube 26 is the same as the ending inner diameter D.sub.I of the journaled end 28.
Referencing FIGS. 3A and 3B, the disadvantages of greater wall thickness and additional mass of a finished part which result from solely using a lathe to cut a journaled end on an extruded tube can be overcome by welding an end cap 32 having a journaled end 34 with an inner diameter D.sub.I, to a body piece 30 having an inner diameter d.sub.I, which is greater than inner diameter D.sub.I. In this regard, the end cap 32 can be welded to a body piece 30, and the end cap 32 machined to a precise outer diameter D.sub.O by a lathe. However, this process has other disadvantages. The end cap 32 is an additional part that requires separate and prior manufacturing. Additionally, this process usually requires the use of special machinery, such as a friction welding machine or inertia welding machine, to weld the end cap 32 to the body piece 30. Finally, the use of this process creates additional manufacturing steps after the end cap 32 has been welded to the body piece 30 and prior to using the lathe to finish the journaled end 34 to a precise outer diameter D.sub.O. The welding of the end cap 32 to the body piece 30 results in a welding bead which requires removal. After the end cap 32 has been welded the body piece 30, and the welding bead removed, the welded end cap 32 and body piece 30 combination should be stressed relieved by heating the combination to cause the molecular composition of the bond 38 between the end cap 32 and the body piece 30 to be consistent throughout the bond 38.